Field of the Invention
The present invention relates to an electroconductive member for electrophotography, a process cartridge and an electrophotographic apparatus.
Description of the Related Art
In an electrophotographic apparatus, that is, an image forming apparatus employing an electrophotographic method, electroconductive members are used for various purposes. For example, such members are used as a charging roller, a developing roller and a transfer roller. It is necessary to control the electrical resistance value of such an electroconductive member used in an electrophotographic apparatus to be 103 to 1010Ω. For this purpose, an electron conducting agent represented by carbon black or an ion conducting agent such as a quaternary ammonium salt compound is incorporated into the electroconductive member.
An electron conducting agent such as carbon black is used as a conducting agent for various electroconductive members because the electrical resistance value is not affected by use environments such as a temperature and a humidity. It is known, however, that if an electroconductive member is provided with conductivity by using an electron conducting agent such as carbon black, there is a possibility that non-uniformity in the electrical resistance value may be caused due to non-uniform dispersion of the electron conducting agent. In particular, it is extremely difficult to prevent sites having a lower electrical resistance value from occurring locally in the electroconductive member due to aggregation of the electron conducting agent.
On the other hand, if an ion conducting agent is incorporated into an electroconductive member, the ion conducting agent is dispersed at the molecular size level, and hence, the non-uniformity in the electrical resistance value can be reduced as compared with the case where an electron conducting agent is used. The resultant electroconductive member has, however, a disadvantage that the electrical resistance value is largely varied depending on the temperature and the humidity of the use environment. In particular, under a low-temperature and low-humidity environment of a temperature of 15° C. and a relative humidity of 10% (hereinafter sometimes referred to as “under the L/L environment”), the electrical resistance value may become high due to drying of the electroconductive member in some cases.
Japanese Patent Application Laid-Open No. H08-272187 proposes a charging member having on an electroconductive substrate an entangled material of electroconductive fiber provided with an electron conjugated polymer. This charging member is free from the non-uniformity in the electrical resistance and shows stable conductivity, and hence, can uniformly electrically charge an electrophotographic photosensitive member as a body to be charged.